In recent years, along with the trend toward higher functionality and a smaller size of electronic equipment such as cellular phones and IC cards, semiconductor devices have been required to have enhanced integration. In order to achieve this, studies have been conducted on finer semiconductors and a stacked structure in which a semiconductor element is stacked onto another.
In the fabrication of the stacked structure, semiconductor elements are bonded by an adhesive. Known adhesives such as acrylic resins, epoxy resins, and silicone resins have, however, heat resistance of as low as about 250° C. and therefore are not usable in steps subjected to high temperatures of 250° C. or higher such as a step of bonding a metal bump to an electrode and an ion diffusion step.
To improve heat resistance, for example, a substrate for thick film technology obtained by forming, on an inorganic insulating substrate that is a glass base material impregnated with a silicone resin, an undercoat containing 30% by volume to 45% by volume of a polyether ether ketone resin powder and a thermosetting resin is disclosed (Patent Document 1).
An adhesive that is used in a flexible printed circuit board and includes a polymer containing a polyimide-based main chain and a functional terminal group having a carbon-carbon triple bond is disclosed (Patent Document 2).
An adhesive composition that includes a polymer containing, in the main chain, a phenyl group, urea, an amido group, and the like, and a functional group having a carbon-carbon triple bond is disclosed (Patent Document 3).
An adhesive composition that includes a polymer containing polyether ether sulfone having a sulfonic group and polyether ether ketone is disclosed (Patent Document 4).